• Aleko Kavouras

What to do Next if Car Fails MD Emissions Test

Updated: Apr 28


Vehicles in Maryland are subject to emissions testing every couple of years. The test only takes a few minutes, and if your car is in good working condition, you are likely to pass.

But what happens if you’ve failed the MD emissions test?


The first step to getting your vehicle to pass emissions testing is to find out what the reason for failure is.


Common Reasons for Vehicle Emissions Test Failure


Hydrocarbon Failure


This can be caused by any of the following:

  1. Air-to-fuel mixture ratio is too rich or too lean

  2. PCV valve malfunctioning

  3. A vacuum leak in the system

  4. Clogged catalytic converter

  5. Engine sensors malfunctioning

Sample Dilution Failure


This occurs when the carbon monoxide and carbon dioxide measurement is under 6% and an accurate exhaust sample cannot be taken from your vehicle. This is usually the indication of a leak in the exhaust system.


On-Board Diagnostics Failure


Your vehicle’s on-board diagnostic system has found malfunctioning emissions control components. A faulty malfunction indicator light on your dashboard could also cause this type of emissions test failure.


Carbon Monoxide Failure


This can be caused by any of the following:

  1. Incorrect idle speed

  2. Clogged air filter

  3. Air-to-fuel mixture is too rich

  4. Engine oil needs changing (is too dirty)

  5. Malfunctioning choke or PCV valve

Emissions Control Equipment Failure


Vehicles are designed with special equipment to control the emissions they produce. If these emissions controls have been removed or disconnected from the vehicle, it will not pass inspection.


Gas Cap Failure


Gas caps aren’t universal – your vehicle’s gas cap was made to fit your gas tank specifically, and if it has been damaged or improperly replaced, it can leak vapors and cause it to fail emissions testing.


All of these possible vehicle issues can be avoided with regular maintenance visits to your local auto mechanic!


What Do You Do With a Failed MD Emissions Test?


If you’re not a professional car mechanic, it’s not easy to figure out on your own which of these is responsible for your vehicle not passing the Maryland emissions test. The quickest and easiest way to get your vehicle in the right condition to pass is to take it to a reliable Maryland auto mechanic. Here, your car will undergo diagnostic testing so that the issue can be found and repaired.


Has your vehicle failed the MD emissions test? Contact the professionals at Hillmuth Auto Care to set up a diagnostic test today!


#exhaust #Maryland #routinemaintenance

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